1. Field of the Invention
The present invention relates to composite high-frequency components and mobile communication apparatuses using the composite high-frequency components. In particular, the present invention relates to a composite high-frequency component which can be used for a plurality of different mobile communication systems and a mobile communication apparatus using the composite high-frequency component.
2. Description of the Related Art
Conventionally, dual band or multiband mobile communication apparatuses which perform communication using a plurality of communication systems corresponding to different frequency bands are used. For example, Japanese Unexamined Patent Application Publication No. 2000-201097 discloses a composite high-frequency component used in such a multiband mobile communication apparatus.
FIG. 1 illustrates a configuration of a high-frequency circuit portion in a mobile communication apparatus using the composite high-frequency component disclosed in Japanese Unexamined Patent Application Publication No. 2000-201097.
This high-frequency circuit is adapted to GSM1800 for the 1800 MHz band (DCS), GSM1900 for the 1900 MHz band (PCS), GSM850 for the 850 MHz band, and GSM900 for the 900 MHz band (EGSM).
In FIG. 1, the section of an antenna switch module 10 is the composite high-frequency component disclosed in Japanese Unexamined Patent Application Publication No. 2000-201097 which is configured as follows.
In FIG. 1, a diplexer 2 separates and combines transmission/reception signals for the GSM850/GSM900 systems and transmission/reception signals for the GSM1800/GSM1900 systems. A transmit/receive switch 3 switches transmission signals and reception signals for the GSM850/GSM900 systems. Similarly, a transmit/receive switch 4 switches transmission signals and reception signals for the GSM1800/GSM1900 systems. A filter 5 lets fundamental waves of transmission signals for the GSM850/GSM900 systems pass and attenuates harmonics of the transmission signals. Similarly, a filter 6 lets fundamental waves of transmission signals for the GSM1800/GSM1900 systems pass and attenuates harmonics of the transmission signals.
When a high-frequency circuit portion (front-end portion) of a mobile communication apparatus is made using this antenna switch module 10, an unbalanced-input-balanced-output SAW is used to make only a reception signal band pass and to remove a signal in an unnecessary frequency band and also to amplify a reception signal using a balanced low-noise amplifier (LNA). In FIG. 1, SAW filters 22 and 23 are filters for allowing reception signals for GSM850 and GSM900 pass, respectively. In addition, a reception signal switch 21 switches reception signals for GSM850 and GSM900. The SAW filters 22 and 23 and the reception signal switch 21 can define a balanced-unbalanced filter module 20.
A transmit/receive switch 7 switches a reception signal for GSM1800 and a reception signal for GSM1900. A SAW filter 41 allows a reception signal for GSM1800 to pass and produces a balanced output. A SAW filter 42 allows a reception signal of GSM1900 to pass and produces a balanced output.
In addition, in order to connect a SAW filter or a module having a SAW filter to the antenna switch module 10, matching circuits 30, 51, and 52 are provided therebetween.
In such a high-frequency circuit portion (front-end portion) which includes three balanced outputs and is compatible with three LNAs (low-noise amplifiers), as illustrated in FIG. 1, the matching circuits 30, 51, and 52 are provided between the antenna switch module 10 and the balanced-unbalanced filter module 20 and between the reception signal switch 7 and the SAW filters 41 and 42, respectively. Therefore, there is a problem in that the size of a mobile communication apparatus (mobile phone) increases because a large number of parts and a large mounting area are required in the overall high-frequency circuit portion.
In addition, it is necessary to adjust matching between the antenna switch module 10 and the balanced-unbalanced filter module 20 and between the antenna switch module 10 and the individual SAW filters 41 and 42. Thus, the design of a mobile communication apparatus is complicated.